Experimental and Theoretical Study of a Quasi-Steady Electron-Beam Plasma in Hot Argon

Aleksandrov, N. L.; Vasil’ev, M. N.; Lysenko, S.L.; Makhir, A. Kh.

doi:10.1134/1.1925792

Cited by 17 publications

(16 citation statements)

References 14 publications

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“…Plasmas with similar characteristics are those created by high-energy electron beams (Elson & Rokni, 1996;Aleksandrov et al, 2005) and by lithographic extreme-ultraviolet (EUV) lasers (with photon energies of 90 eV and higher) (Beckers et al, 2016). All of these have in common the lack of an applied electric field and a high-energy particle beam as the plasma source.…”

Section: Introductionmentioning

confidence: 99%

“…These plasmas are usually modelled by fluid models in which the transport equations for the particle and energy densities are solved for given boundary conditions (Elson & Rokni, 1996;Aleksandrov et al, 2005). The transport coefficients are calculated assuming a certain electron energy distribution function, or creating a collisional-radiative model for the electron population.…”

Section: Introductionmentioning

confidence: 99%

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Hybrid modelling of a high-power X-ray attenuator plasma

Ortega

Lacoste

Minea

2018

J Synchrotron Radiat

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X-ray gas attenuators act as stress-free high-pass filters for synchrotron and free-electron laser beamlines to reduce the heat load in downstream optical elements without affecting other properties of the X-ray beam. The absorption of the X-ray beam triggers a cascade of processes that ionize and heat up the gas locally, changing its density and therefore the X-ray absorption. Aiming to understand and predict the behaviour of the gas attenuator in terms of efficiency versus gas pressure, a hybrid model has been developed, combining three approaches: an analytical description of the X-ray absorption; Monte Carlo for the electron thermalization; and a fluid treatment for the electron diffusion, recombination and excited-states relaxation. The model was applied to an argon-filled attenuator prototype built and tested at the European Synchrotron Radiation Facility, at a pressure of 200 mbar and assuming stationary conditions. The results of the model showed that the electron population thermalizes within a few nanoseconds after the X-ray pulse arrival and it occurs just around the X-ray beam path, recombining in the bulk of the gas rather than diffusing to the attenuator walls. The gas temperature along the beam path reached 850 K for 770 W of incident power and 182 W m of absorbed power. Around 70% of the absorbed power is released as visible and UV radiation rather than as heat to the gas. Comparison of the power absorption with the experiment showed an overall agreement both with the plasma radial profile and power absorption trend, the latter within an error smaller than 20%. This model can be used for the design and operation of synchrotron gas attenuators and as a base for a time-dependent model for free-electron laser attenuators.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hybrid modelling of a high-power X-ray attenuator plasma

Ortega

Lacoste

Minea

2018

J Synchrotron Radiat

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“…It was concluded that the triatomic molecular ions Ar 3 + play important role at high pressure. Aleksandrov et al [8] constructed a kinetic model to compute the stationary plasma density in hot argon. The gas pressure and the electron beam current were varied in the range of 1-50 Torr and 1-50 mA, respectively.…”

Section: Introductionmentioning

confidence: 99%

Investigations on the time evolution of the plasma density in argon electron-beam plasma at intermediate pressure

Chen¹,

Li²,

Liu³

2017

Plasma Sci. Technol.

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The time evolution of the argon electron-beam plasma at intermediate pressure and low electron beam intensity was presented. By applying the amplitude modulation with the frequency of 20 Hz on the stable beam current, the plasma evolution was studied. A Faraday cup was used for the measurement of the electron beam current and a single electrostatic probe was used for the measurement of the ion current. Experimental results indicated that the ion current was in phase with the electron beam current in the pressure range from 200 Pa to 3000 Pa and in the beam current range lower than 20 mA, the residual density increased approximately linearly with the maximum density in the log-log plot and the fitting coefficient was irrelative to the pressure. And then three kinds of kinetic models were developed and the simulated results given by the kinetic model, without the consideration of the excited atoms, mostly approached to the experimental results. This indicated that the effect of the excited atoms on the plasma density can be ignored at intermediate pressure and low electron beam current intensity, which can greatly simplify the kinetic model. In the end, the decrease of the plasma density when the beam current was suddenly off was studied based on the simplified model and it was found that the decease characteristic at intermediate pressure was approximate to the one at high pressure at low electron beam intensity, which was in good accordance with the experimental results.

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“…However, to our knowledge, previous experimental studies have considered only the overall X-ray absorption and temperature of the gas (Requardt et al, 2013;Herná ndez, 2010) or the heat transfer following the power absorption (Feng et al, 2016), but none of them have attempted to measure or model the ionization and recombination within the gas. The basic physics of the attenuator may be similar to that encountered in electronbeam (Aleksandrov et al, 2005;Elson & Rokni, 1996) or extreme ultraviolet plasmas (Beckers et al, 2016), although the specific differences with these sources, like the coupling between photon absorption and gas density or the pressure range of operation, call for a specific study on the attenuator plasma.…”

Section: Introductionmentioning

confidence: 99%

Characterization of X-ray gas attenuator plasmas by optical emission and tunable laser absorption spectroscopies

Ortega¹,

Lacoste²,

Béchu³

et al. 2017

J Synchrotron Radiat

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X-ray gas attenuators are used in high-energy synchrotron beamlines as high-pass filters to reduce the incident power on downstream optical elements. The absorption of the X-ray beam ionizes and heats up the gas, creating plasma around the beam path and hence temperature and density gradients between the center and the walls of the attenuator vessel. The objective of this work is to demonstrate experimentally the generation of plasma by the X-ray beam and to investigate its spatial distribution by measuring some of its parameters, simultaneously with the X-ray power absorption. The gases used in this study were argon and krypton between 13 and 530 mbar. The distribution of the 2p excited states of both gases was measured using optical emission spectroscopy, and the density of argon metastable atoms in the 1s state was deduced using tunable laser absorption spectroscopy. The amount of power absorbed was measured using calorimetry and X-ray transmission. The results showed a plasma confined around the X-ray beam path, its size determined mainly by the spatial dimensions of the X-ray beam and not by the absorbed power or the gas pressure. In addition, the X-ray absorption showed a hot central region at a temperature varying between 400 and 1100 K, depending on the incident beam power and on the gas used. The results show that the plasma generated by the X-ray beam plays an essential role in the X-ray absorption. Therefore, plasma processes must be taken into account in the design and modeling of gas attenuators.

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Experimental and Theoretical Study of a Quasi-Steady Electron-Beam Plasma in Hot Argon

Cited by 17 publications

References 14 publications

Hybrid modelling of a high-power X-ray attenuator plasma

Hybrid modelling of a high-power X-ray attenuator plasma

Investigations on the time evolution of the plasma density in argon electron-beam plasma at intermediate pressure

Characterization of X-ray gas attenuator plasmas by optical emission and tunable laser absorption spectroscopies

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